I'd like to amend my comment; I've read further in the Cambridge Handbook and found this quote:

"Recent research has suggested a qualification on this rule of thumb. For instance, Hoffman, Coffey, and Ford (2000) found that even junior journeymen weather forecasters (individuals in their early 30s) can have had as much as 25,000 hours of experience. A similar figure seems appropriate for the domain of intelligence analysis (Hoffman, 2003a)."